Production of nitric acid



I K.'B. QU'INAN. I PRODUCTION'OF NITRIC ACID. APPLICATION FILED FEB- 24. 1919.

I 1,355,357. Patented Oct. 12,1920.

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yawm-fi ATTORNE K.B.QUINAN PRDDUGTION or unmc ACID.

APPLICATION FILED FEB. 24. 1919.

1,355,357. Patented 0013. 12,1920.-

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m x y vmns .Mz; rm ATTORNEY K..B. QUINAN.

PRODUCTION OF NITRIC ACID. APPIJCATION FILED FEB. 24, I919.

1,355,357. Patented Oct. 12, 1920.

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ATTORNEY I UNITED STATES Pir-ENT"oFFIcii-.f

KENNETH DING-HAM QUINAN, or SOMERSET WEST, car PROVINCE, so -T AFRIGL rnonucrron or m'rmc ACID.

To all whom it may concern Be it known that I, KE NETH BINGHAM QUINAN, a citizen of the United States of America, and residing at Somerset West, Cape Province, Union of South Africa, have invented certain new and useful Improvementsin and Relating to the Production of Nitric Acid, of which the following is a specification.

This invention relates to the production of nitric acid from gases containing oxids of nitrogen andis'more particularly concerned with the synthetic production of ni' tric acid. I

The processes for the synthetic production of nitric acid may be divided .into twoclasses, the first of which involves the direct oxidation of nitrogen to nitric oxid and the second, the production and subsequent oxidation of ammonia; w

In processes ofboth classes, nitric oxid is formed and this nitric oxid requires to be oxidized to nitrogen peroxid N0 which is then caused to react with water, producing nitric acid and nitric oxid.

A characteristic of processes of the first class is that the product of oxidation of the will yield a product atmospheric nitrogen-is a gaseous mixture having a low content of oxids of nitrogen, the ,content being equivalent to between 1% and 2 per cent. of nitric oxid, while processes of thesecond class yield gaseous mix, tures considerably richer in oxids of nitrogen. In processes of this class roughly 1 volume of ammonia is mixed with 10 vol- I I considerable both 1n consequence of the maumes of air and the mixture on oxidation per cent. of oxids of nitrogen, expressed is required to be oxidized to nitrogen peroxid according to the equation a I 2NO 1-Q :2NO +26900 cals. I The gases containing nitrogenperoxid, in

action, are preferably cooled to a suitable I temperatureprior to bringing them into contact with water 1n acid according to the equat1on 1 cN0,+2H,0=4HNO,+2N0+496 0 Gal 'As will be observed, only four-sixths of ithe'amount oinitrogen peroxid is converted .55 into nitric acid, the remaining two molecontaining roughly 10 order to produce nitric Specification of Letters Patent. Pate t d O t 12 1920.

Application filed February 24, 19 19. Serial No. 278,896. I

by the liquid absorbent, water or dilute nitric acid, as the case may be, has hitherto been effected 1n absorption towers or in ab- 'sorption chambers arranged singly or in se- 1 ries or parallel or series parallel and in some or all of which refractory packing is 'j'contained. The aqueous absorbent and the gases are passed; in counter-current through these towers and when the towers or cham- "bers are arranged in series, the absorbent is pumped from the base of each tower or "chamber of the series to the head of the next succeeding tower or chamber. -"-Both of the reactions indicated above proceed with a' velocity whicl more or less varies directly as the concentration of oxids 'of nitrogen in "the gases, i. e, to their partial pressures and it therefore follows that in the initial than in the final towers of the LSBIIBS. With towers of any considerable proportions it is impossible to control the terialsemployed in their construction and the character of the foundations required to support their very great weight.

-The present invention consists in effecting repeated contacts between the gases containing oxids of nitrogen, and the aqueous absorbent, by distributing the aqueous absorbent over the surfaces of permeable diaphragms, through which the gases are caused to pass under such conditions that substantial percolation of the absorbent through the permeable diaphragms is prevented.

As permeable diaphragms, plates provided with a large number of holes of a suitable size to enable the absorbent and the gas to be brought into intimate contact, are emplolyed. l I

he diaphragms above the other in asuitable container, or a may be arranged one I the reactions take place much more rapidly plurality of containers may be employed, in

si'ngle diaphragm is arphragm, the space below the succeeding diaphragm and the intervening gas connections, if any. If desirable or necessary, however,

separate chambers may be arranged between successive diaphragms, so that the gases may,

- be caused to traverse the chambers between the contact stages.

Suitable apparatus for carrying the invention into effect is illustrated by way-of example in the accompanying drawings, in

- which Figure 1 representsfin plan, a suitable arrangement of plant, and

Fig. 2 is an end elevation, and I Fig. 3 is a -'front elevation thereof; while Figs. 4, 5 and 6 illustrate suitable constructions of devices empl ye'd as absorbers.

In the drawings, '1, 1, the'conduits for leading the gases containing oxids of nitrogen into the absorbers, 2, 2,

2", 2 and 2 respectively, while 3, 3, 3", 3 andv 3 are the conduits leading the gases from the absorbers after they have passed through the liquid therein.

The devices 4, 4*, 4 and 4 are oxidation chambers which may be of any suitable construction, and which are provided for the purpose of enabling the lower oxids of nitrogen to become oxidized to nitrogen dioxid by means of the free oxygencontailled 1r in the gases due to the presence of therein, and to the reaction between the nitrogen dioxid and the water which takes place in the absorbers.

The conduit 1 serves to bring the oxide-of nitrogen from the apparatus in which they are formed by, forinstance, the catalytic oxidation of ammonia, while the conduits 1, 1", 1 and 1? conduct the gases from the oxi-' dizing chambers to the relative absorption chambers and the conduits 3, 3, 3",3 lead the gases from the absorption chambers to the relative oxidation chambers, while the conduit 3, conveys the gases which have been substantially or entirely freed from oxids of nitrogen to the atmosphere.

Circulating tanks5, 5, 5", and 5 and 5 are provided, and these tanks are connect- ;ed respectively by pipes '6, 6 ,6", 6. and

6. with pumps 7, 7, 7', 7. and 7 the delivery sides of which are connected by pipes 8, 8,

8 8 a1id8 with the. absorbers Q, 2", 2", 2 and .2' respectively, in such manner that they deliver the liquid on to the surfaces of the diaphragms therein. Pipes 9, 9, 9 9 and 9 convey the liquid from these diaphragms through coolers 10, 10, 10, 10 and 10 back i to the respective tanks.

Into the tank 5 water is fed at the desired rate by the pipe 119, and from this tank the liquid passes when it reaches the level of the pipe 11 to the next tank, the pipes 11, 11 and 11 similarly conveying any excess of liquid from a preceding to a succeeding tank, hile the acid finally leaves the system by the pipe 11.-

Referring to Figs. 4, 5 and 6, which illustrate suitable devices employed as absorbers,

12 indicates the walls of the absorption chambers 13, and in the case of the construc tion shown in Fig. 5, 13 the diaphragms therein, 14 the inlet for the liquid, 15 the outlet therefor, 16 the gas inlet and 17 the corresponding outlet.

In the construction illustrated in Fig. 4,

the gas inlet 16 passes through the cover of the absorption chamber and extends down- -wardly to the perforated diaphragm 13 into the space below which it delivers the gases,

which pass from this space through the liquid supplied to its surface by the pipe 14 and led away therefrom by the pipe 15, the gases after having passed through the liquid leaving by way of the pipe 17.

In the construction shown in Fig. 5, two

diaphragms 13 and 13 are provided, a trap 18 being provided in the absorber for conveying the liquid descending from the diaphragm 13 on to the diaphragm 13., In this construction, as will be understood, the gas passes successively through the bodies of liquid supported on the diaphragmsj In the construction illustrated in Fig. 6, a

pipe 19 with its edge extending above the surface-of the diaphragm 13 is arranged to enable the liquid to flow over. the edge of the pipe 19 down into the cup 20 over the edge 'of which the'liquid will flow in turn into the base of the absorber from which it will be led away 'by the liquid outlet 15.

.The construction of the oxidation cham bers may vary within wide limits but, as the time of oxidation may be considered to vary inversely as the intimacy of mixing which can be efiected in the chambers, it is generally speaking desirable to so construct these chambers as to aid in securing intimacy of mixture of the gases treated therein.

This result may be achieved, for instance, by providing means within the chambers for dividing up the gases introduced, into a number of'currents as, for instance, by a1"- ranging in the chambers a plurality of perforated diaphragms or by packing of suitable form.

providing therein As will be understood, in orderthat si1b-. W

stantial percolation of the liquid through the perforations the diaphragms may be prevented, it is necessary that the difference 1n pressure between the gas below the diaphragms and that above shall be sufiicient to cause the gas, to pass upwardly through the perforations in the diaphragms and through the body of liquidsupportedthereon at a suitable velocity. This difference in L pressure will depend upon the density and 4 however, be'stated that diaphragms 11; inch.

thick and having holes inch in diameter, may be employed.

Having now described my invention, what I claim as new and desire to secure byLet-' ters Patent is The process of producin nitric acid from V .gases containing oxids o nitrogen, which consists in effecting repeated contacts between the gases containing oxids of. nitrogen and the liquid absorbent, by distributing the liquidabsorbent over the surfaces of permeable diaphragms through which the gases are caused to pass under such conditionsas regards velocity that substantial percolation of the 'absorbentthrough the permeabl dia hragms is prevented.

n testimony whereof name to this specification.

KENNETH BINGHAM QUINAN.

I have; signed my. 

